JP2004009601A - Preform for fiber reinforced plastic and method for producing the same - Google Patents

Abstract

An object of the present invention is to provide a preform for FRP which can sufficiently prevent a decrease in strength of an obtained FRP, can be easily shaped, and can maintain a shape after shaping, and a method for manufacturing the same.
According to the present invention, a plurality of beams including a thermoplastic resin are passed through a laminated body in which a sheet portion made of reinforcing fibers is laminated, and then the laminated body is heated and melted. This is a manufacturing method of the preform 2 to be shaped. In this case, the beam 8 can freely adjust the amount of the thermoplastic resin suitable for maintaining the shape of the laminated body after shaping. Therefore, by penetrating the beam 8 into the laminate 4 and melting it by heating, the laminate 4 can be impregnated with the thermoplastic resin regardless of the skill level of the operator without excess or shortage. Further, since the melting and curing of the beam 8 is controlled only by heat, the laminated body 4 can be shaped at an arbitrary timing after the melting of the beam 8, and after shaping, the laminated body 4 at the time of shaping is formed by the cured thermoplastic resin. The shape is retained.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a preform for a fiber reinforced plastic (FRP) used as a reinforcing material when producing a fiber reinforced plastic (FRP) and a method for producing the same.
[0002]
[Prior art]
Fiber-reinforced plastics (hereinafter referred to as "FRP") are intended to reinforce the mechanical strength of plastics by introducing reinforcing fibers into the plastics, and have advantages such as light weight and impact resistance. And are used in various fields such as aircraft and automobiles.
[0003]
As a method for producing such an FRP, a resin transfer molding (RTM) method in which a preform is placed in a mold, and the inside of the mold is depressurized and resin is injected is well known.
[0004]
A preform used in such an RTM method is used as a reinforcing material when manufacturing an FRP. As a method for producing the preform, conventionally, a plurality of sheet-like reinforcing fiber bodies (dry-reinforced fiber) have been used. There has been known a method of laminating a laminate obtained by laminating fibrous bodies) while applying a small amount of glue, and shaping the laminate by applying pressure using a vacuum bag or the like to produce a preform.
[0005]
[Problems to be solved by the invention]
However, the conventional method for manufacturing a preform described above has the following problems.
[0006]
That is, in the above-mentioned production method, a rubber-based emulsion is usually used as the sizing agent, and when the sizing agent is applied, the sizing agent is sprayed on the laminate. For this reason, the amount of the paste applied varies depending on the skill of the operator, and the following problem has occurred.
[0007]
In other words, when the coating amount is excessive, even if a thermosetting resin serving as a matrix is injected to produce an FRP product, if the curing shrinkage of the thermosetting resin is large, cracks occur in the glue portion, which is obtained. The mechanical strength of the FRP product may be reduced. On the other hand, if the amount of application is small, even if the laminated body of the reinforcing fiber body is shaped into a desired shape, the laminated body returns to the original shape, and it becomes difficult to maintain that shape.
[0008]
Further, when the paste is sprayed on the reinforcing fiber laminate, the paste usually cures in several minutes because a highly volatile dispersion solvent is used. For this reason, there is also a problem that it is difficult to shape the laminate into a desired shape unless the laminate is shaped in a short time after applying the paste.
[0009]
The present invention has been made in view of the above circumstances, and can sufficiently prevent a decrease in mechanical strength of an obtained FRP product, can easily shape a preform, and maintain a shape after shaping. An object of the present invention is to provide a manufacturing method and a preform for FRP.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes a plurality of beams including a thermoplastic resin penetrating a laminate including a plurality of sheet portions made of reinforcing fibers and laminating the plurality of sheet portions. And a shaping step of shaping the laminate by heating and melting the beam.
[0011]
According to the present invention, when the beam is melted by heating, the thermoplastic resin is impregnated in the laminate. At this time, the amount of the thermoplastic resin suitable for maintaining the shape of the laminated body after shaping can be adjusted by the amount of the thermoplastic resin contained in one beam and the number of beams. Therefore, by passing the beam through the laminate and melting it by heating as in the present invention, it is possible to impregnate the laminate with the thermoplastic resin regardless of the skill level of the operator, and without excess or shortage. Further, since the melting and curing of the beam is controlled by the applied heat, the beam maintains a molten state without being cured when heat is applied. Therefore, if heat is applied, the thermoplastic resin does not harden before shaping, and it becomes possible to shape the laminate at an arbitrary timing after the beam is melted. After the shaping, the thermoplastic resin is hardened by cooling the thermoplastic resin, and the shape of the laminate at the time of shaping is maintained by the hardened thermoplastic resin. Further, since the laminate is impregnated with a thermoplastic resin having a small curing shrinkage, even if an FRP product is manufactured by injecting a thermosetting resin having a large curing shrinkage into a preform, the generation of the resin cracks is not sufficiently caused. Thus, a decrease in the mechanical strength of the FRP product can be sufficiently prevented.
[0012]
In the above manufacturing method, it is preferable that the beam further includes a reinforcing fiber along a direction in which the beam extends.
[0013]
In this case, the reinforcing fibers are easily knitted three-dimensionally into the laminate by passing the beam through the laminate. Therefore, a three-dimensional reinforcing effect can be obtained for the preform.
[0014]
Further, the present invention is a preform for FRP manufactured by the above manufacturing method. In this preform for FRP, the voids are filled in the laminate with a thermoplastic resin having a small curing shrinkage. Therefore, even if an FRP product is manufactured by injecting a thermosetting resin into the preform, cracking of the resin may occur. Occurrence is sufficiently prevented, and a decrease in the mechanical strength of the FRP product can be sufficiently prevented. The melting and curing of the thermoplastic resin contained in the preform is controlled only by the applied heat. Therefore, once the preform is manufactured, the shape of the preform can be changed as many times as necessary.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0016]
FIG. 1 is a partial sectional view schematically showing an embodiment of an FRP preform according to the present invention. As shown in FIG. 1, a preform for FRP (hereinafter simply referred to as “preform”) 2 includes a laminate 4, and the laminate 4 is configured by laminating a plurality of sheet parts 3. I have.
[0017]
Each sheet part 3 forms the basic skeleton of the preform 2 and is made of reinforcing fibers 3a. The sheet portion 3 is made by, for example, plain weaving or twill weaving of the reinforcing fibers 3a. The reinforcing fibers 3a are made of fibers constituting a normal FRP, such as glass, carbon, and aramid fibers.
[0018]
The preform 2 contains a cured thermoplastic resin 5. The thermoplastic resin 5 functions as a glue for adhering the adjacent sheet portions 3 and maintaining the shape of the laminate 4 in a predetermined shape.
[0019]
The thermoplastic resin 5 is not particularly limited as long as it has the above-mentioned function, but the thermoplastic resin 5 has a low crystallinity such as nylon (PA), polyvinyl alcohol (PVA), polyetherimide (PEI), or the like. In addition, a resin having a high affinity with the FRP matrix resin such as an epoxy resin is preferable.
[0020]
In the preform 2, since the thermoplastic resin 5 having a small curing shrinkage is impregnated in the laminate 4, a thermosetting resin having a large curing shrinkage is injected into the preform 2 to produce an FRP product. Also, the occurrence of resin cracks can be sufficiently prevented, and a decrease in the mechanical strength of the FRP product can be sufficiently prevented. The melting and curing of the thermoplastic resin 5 can be freely adjusted only by heat. Therefore, even after the preform 2 is manufactured once, the shape of the preform 2 can be changed by heating, and the changed shape can be maintained by cooling. Therefore, for example, even if the shape of the preform 2 collapses during transportation, the preform 2 can be restored to the original shape by heating and cooling.
[0021]
Next, a method for manufacturing the above-described preform 2 will be described.
[0022]
As shown in FIG. 2, first, a plate 6 having a plurality of holes 6a is prepared. Then, a plurality of sheet portions 3 made of reinforcing fibers are laminated on the plate 6, and the laminate 4 is formed on the plate 6.
[0023]
Next, a plurality of hollow needles 7 are radiated perpendicularly to the laminate 4, and are pushed until their tips enter the holes 6 a of the plate 6, thereby causing the needles 7 to penetrate the laminate 4.
[0024]
Here, it is preferable that the plurality of needles 7 are fixed to one surface of the plate. In this case, a plurality of needles 7 can be collectively penetrated through the laminated body 4, and the operation of penetrating the needles 7 is performed more efficiently than a case where a plurality of needles 7 are penetrated through the laminated body 4 one by one. be able to.
[0025]
Next, a beam 8 made of a thermoplastic resin is made to penetrate the laminate 4. In this case, by inserting the beam 8 into the inside of the needle 7, a plurality of beams 8 penetrate the stacked body 4. Here, the number of the beams 8 penetrated through the laminate 4 depends on the amount of the thermoplastic resin contained per one beam and the total amount of the thermoplastic resin suitable for maintaining the shape of the laminate 4 in a predetermined shape. It is determined. Therefore, it is possible to impregnate the laminate 4 with the thermoplastic resin regardless of the skill level of the worker and without any excess or shortage.
[0026]
After the beam 8 has penetrated the laminate 4 in this manner, the needle 7 is pulled out of the laminate 4. Thereby, as shown in FIG. 3, a plurality of beams 8 pass through the stacked body 4 (beam penetration step).
[0027]
Next, the laminate 4 is given the general shape of the FRP product. Therefore, the laminated body 4 is arranged on a simple type, a core, or the like, and is heated to a temperature at which the beam 8 is softened without melting, and conforms to the general shape of the FRP product.
[0028]
Subsequently, the laminate 4 is hermetically sealed by covering the entire laminate 4 with a nylon bag or the like, and the beam 8 is heated and melted while reducing the pressure in the bag (melting step, shaping step). Thus, the laminate 4 is pressed by the bag to shape the laminate 4 into a desired shape.
[0029]
At this time, since the thermoplastic resin is in a molten state, the laminate 4 can be easily shaped. Here, since the melting and curing of the beam 8 is controlled only by the applied heat, the beam 8 maintains a molten state without being cured as long as heat is applied. Therefore, the resin is not cured before shaping as long as heat is applied to the beam 8, and the laminated body 4 can be shaped at an arbitrary timing after the beam 8 is melted.
[0030]
After shaping, the thermoplastic resin is cured by cooling the thermoplastic resin, and the cured thermoplastic resin holds the laminate 4 in the shape at the time of shaping. Further, since voids in the laminate 4 are filled with a thermoplastic resin having a small curing shrinkage, even if a thermosetting resin such as an epoxy resin is injected into the preform 2 to produce an FRP product, resin cracks may occur. Is sufficiently prevented, and a decrease in the mechanical strength of the FRP product can be sufficiently prevented.
[0031]
Next, a second embodiment of the method for manufacturing a preform according to the present invention will be described.
[0032]
The manufacturing method of the present embodiment differs from the manufacturing method of the first embodiment in that the beam 8 further includes a reinforcing fiber 9 along the extending direction thereof, as shown in FIG. In this case, the reinforcing fibers 9 are three-dimensionally woven into the laminate 4 by passing the beam 8 through the laminate 4.
[0033]
Conventionally, as a method of manufacturing a preform, a method of three-dimensionally knitting reinforcing fibers and making the shape substantially the same as the shape of the FRP product is also known, and large-scale dedicated equipment is required to implement this method. It took a lot of manufacturing time. However, by including the reinforcing fibers 9 in the beam 8 in the extending direction and penetrating the beam 8 through the laminate 4 as in the present embodiment, the reinforcing fibers are three-dimensionally woven into the laminate 4. Therefore, a three-dimensional reinforcing effect can be obtained. When the beam 8 is heated to the softening temperature of the thermoplastic resin, the shapeability is improved. For this reason, it is not necessary to braid the reinforcing fiber three-dimensionally and make it almost the same shape as the FRP product as in the conventional method, and it is not necessary to use a large-scale dedicated facility and a large amount of manufacturing time.
[0034]
Further, in the above-described conventional method, since the fibers are three-dimensionally entangled, a large void is formed between the fibers in the preform as compared with a case where the fibers are not three-dimensionally entangled. For this reason, when a thermosetting resin is injected into a preform to produce an FRP product, if the thermosetting resin has a large curing shrinkage, a resin crack may occur in that portion, and mechanical properties may be reduced. However, by heating and melting the beam 8 as in the present embodiment, the voids between the fibers in the laminate 4 can be filled with the thermoplastic resin. Even if the FRP product is manufactured by injecting, it is possible to sufficiently prevent the occurrence of resin cracks that affect the product strength.
[0035]
The present invention is not limited to the first and second embodiments described above. For example, in the first and second embodiments, the needle 7 is used to penetrate the beam 8 through the laminate 4, but the needle 7 is used to facilitate the penetration of the beam 8. However, it is not always necessary in the preform manufacturing method of the present invention. Therefore, the beam 8 may directly penetrate the laminate 4.
[0036]
Further, in the above embodiment, the beam 8 penetrates the stack 4 vertically, but it is sufficient that the beam 8 penetrates the stack 4. Therefore, the beam 8 penetrates the stack 4 obliquely. May be.
[0037]
Further, in the above embodiment, the stacked body 4 is shaped while the beam 8 is heated and melted. However, the stacked body 4 may be shaped after the beam 8 is heated and melted.
[0038]
Further, in the above-described embodiment, a plurality of sheet portions 3 are stacked, but a plurality of sheet portions may be stacked by folding one sheet made of a reinforcing fiber and having a plurality of sheet portions. .
[0039]
Further, in the above-described embodiment, the preform 2 is manufactured by the RTM method. However, the preform 2 is not limited to the RTM method. It can be manufactured by a hand lay-up method of shaping the beam 8 while melting it.
[0040]
Next, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0041]
【Example】
(Example 1)
First, 20 carbon fiber plain weaves (300 mm × 300 mm) were prepared. In the carbon fiber plain weave, T300 3K was used as the carbon fiber, and the fold pitch was about 2 mm.
[0042]
On the other hand, a flat metal plate having a thickness of 10 mm and a plurality of prepared holes having an inner diameter of 2 mm and a depth of 1 mm was prepared. In the metal plate, a plurality of pilot holes were formed in a lattice shape, and the pitch of the pilot holes was 20 mm.
[0043]
Then, a carbon fiber plain weave laminate was placed on the metal plate.
[0044]
Further, a plate with a needle was prepared. In the plate with needles, a plurality of hollow needles were arranged in a grid on the plate, and the pitch of the needles was 20 mm. The outer diameter of the needle was 1.5 mm and the inner diameter was 1.1 mm. The needle-attached plate was pushed into the weave (the portion where warp and weft interlaced) with the needle facing the laminate side, and the needle-attached plate was pushed until the tip was inserted into the prepared hole of the metal plate.
[0045]
On the other hand, after the PA (nylon) raw material was melted, the raw material was extruded from a plurality of nozzles having a hole having an inner diameter of 1 mm, cooled, and cut into 4 mm to obtain a PA beam (φ1 mm, length 4 mm). Then, after inserting this beam into the needle, the plate with the needle was removed from the laminate.
[0046]
Subsequently, a metal plate preheated to 230 ° C. was pressed against the laminate for about 1 minute to heat and melt the beam, and then the metal plate was removed and cooled as it was to obtain an original preform. .
[0047]
This preform raw material was pressed against a male mold having a predetermined shape, heated with an iron, and shaped to obtain a preform. When the preform was left for one hour, the shape was hardly changed.
[0048]
Finally, the preform was placed in a predetermined mold, and after epoxy resin was injected, the preform was heated and cured to obtain an FRP having a predetermined shape. When the mechanical strength of this FRP was measured, the mechanical strength was 880 MPa in bending strength and 64 MPa in interlaminar shear strength, which were 33% and 41% higher than those coated with a rubber-based paste. The mechanical properties were based on JIS standards (bending: JIS K 7074, interlaminar shearing: JIS K 7078).
(Example 2)
Except that a carbon fiber in which the PA fiber is commingled (mixed) is formed through a die having a hole with an inner diameter of 1 mm and heated to 230 ° C. (pultrusion molding), and this is cut into 4 mm to obtain a beam. A preform was produced in the same manner as in Example 1. When the preform was left in the same manner as in Example 1, the shape was hardly changed.
[0049]
Using this preform, an FRP having a predetermined shape was produced in the same manner as in Example 1. When the compression strength after impact (CAI) as the mechanical strength of this FRP was measured, the CAI was about 400 MPa. In addition, the measurement of the compressive strength after impact was based on SACMA SRM2.
[0050]
【The invention's effect】
As described above, according to the method for manufacturing a preform for FRP of the present invention, the amount of thermoplastic resin suitable for maintaining the shape of the laminated body after shaping can be adjusted by the beam. Regardless of the degree, the thermoplastic resin can be impregnated into the laminate without excess or shortage. Therefore, even if a FRP product is manufactured by injecting a thermosetting resin into a preform, the occurrence of resin cracks can be sufficiently prevented, and a decrease in mechanical strength can be sufficiently prevented. In addition, since the melting and curing of the beam is controlled only by heat, it is possible to shape the preform at any timing as long as the beam is heated. Further, after shaping, the thermoplastic resin is cured by cooling, so that the preform can be maintained in a desired shape after shaping.
[0051]
In addition, according to the preform for FRP of the present invention, since the thermoplastic resin with small curing shrinkage is impregnated in the laminate, even if the thermosetting resin is injected into the preform to produce an FRP product, The occurrence of cracks can be sufficiently prevented, and a decrease in mechanical strength can be sufficiently prevented. Furthermore, the viscosity of the thermoplastic resin can be freely adjusted by heating and cooling. Therefore, once the preform is manufactured, the shape of the preform can be changed as many times as necessary.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing one example of an FRP preform of the present invention.
FIG. 2 is a perspective view showing an initial step of a method of manufacturing a preform for FRP of the present invention.
FIG. 3 is a perspective view showing a state where a beam penetrates a laminate.
FIG. 4 is a partial sectional view showing another embodiment of the beam.
[Explanation of symbols]
2 ... preform, 3 ... sheet part, 4 ... laminate, 5 ... thermoplastic resin, 8 ... beam, 9 ... reinforcing fiber.

Claims (3)

A beam penetration step of penetrating a plurality of beams including a thermoplastic resin for a laminate including a plurality of sheet portions made of reinforcing fibers and laminating the plurality of sheet portions,
A melting step of heating and melting the beam,
A shaping step of shaping the laminate,
A method for producing a preform for fiber reinforced plastic, comprising: The method for manufacturing a preform for a fiber reinforced plastic according to claim 1, wherein the beam further includes reinforcing fibers along a direction in which the beam extends. A preform for a fiber-reinforced plastic manufactured by the method for manufacturing a preform for a fiber-reinforced plastic according to claim 1.

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